1. Field of the Invention
The present invention relates to a regenerative repeater, and more particularly to a regenerative repeater for amplitude control and chronological control of an n stage digital signal having a high transmission speed with at least one clock D flip-flop and a differential amplifier having n-1 threshold voltages.
2. Description of the Prior Art
Through the combination of digital time-division multiplex signals of a low hierarchial stage, and hence of a slower transmission speed, into such of a higher hierarchial stage, and through the introduction of digital message switching technology, the necessity arises of constructing transmission paths with a very high data signaling rate. Transmission paths of this type have data signaling rates in the range of several hundred M Baud, corresponding to a CCITT recommendation, in particular, such as 565 M Baud. Because of the rather high cable attenuation at these frequencies, it is necessary to introduce into the transmission path, at comparatively small intervals, regenerative repeaters for regenerating the transmitted signal, whereby considerable requirements are made of such repeaters with respect to the signal processing speed. In order to increase the transmission capacity with the same transmission speed, use is made of the possibility of transmitting multi-stage signals instead of binary signals. In the case of the transmission of multi-stage signals, the requirements made of regenerative repeaters further increase; in view of the difficulties in realizing multilevel logic circuits, a regeneration method has proven successful in which the multi-stage signals are converted into unipolar pulse trains and the latter are respectively separately regenerated.
Regenerators for the amplitude and chronological regeneration of multi-stage digital signals are known in the art. From the German published application 28 27 958, a regenerative repeater for multi-stage digital signals at a high transmission speed--present in a partial-response code--is known. This regenerative repeater contains, at the input side, a level switch with a sampling stage by means of which the signals arising are divided into respectively two pulse trains having different amplitude ranges, and, moreover, a chronological regeneration is performed. For the purpose of amplitude decision, the two signal parts are separated into binary signals which are regenerated according to amplitude in the individual stages of an amplitude decision element containing tunnel diodes. From the German published application No. 28 33 267 a method is also known for regenerating a multi-stage digital signal having components occurring in the GHz range, and a corresponding regenerative repeater. The regenerative repeater contains a special bistable flip-flop, equipped with tunnel diodes, to which the signal to be regenerated is supplied with such an amplitude that only upon occurrence of a set pulse does a switch over of the bistable flip-flop take place. For multi-stage digital signals, several bistable flip-flops of this type, which are respectively effective in a different amplitude range, are connected in parallel.
The above-mentioned regenerative repeaters offer the possibility of regenerating digital signals with a plurality of, for example, seven, amplitude levels. The expense required for this purpose is not justified in the case of regeneration of four-level digital signals; moreover, a greater number of circuit elements also requires an altogether higher operating current; and, in addition, a higher signal transit time can result.
After completed regeneration, the individual signal portions, for example by way of an assessed addition, are joined together to form a new signal.
In an earlier patent application, a regenerative repeater is disclosed for the purpose of amplitude regeneration and chronological regeneration of a quaternary pulse code modulated (PCM) signal having a high transmission rate, and for the purpose of its conversion into two PCM signals present in a binary code which is as redundancy-poor as possible, in particular, the dual code. This regenerative repeater is characterized in that there is connected, with a connection for the quaternary signals to be regenerated, a signal input of a first differential amplifier, whose signal output is connected to the D input of a first clocked D flip-flop, that there is, moreover, connected with the output terminal for the quaternary signals, the input of a first delay arrangement having a delay time corresponding to the signal transit time through the first differential amplifier and the first D flip-flop. The signal input of a second differential amplifier is connected to the output of the first delay arrangement, the second differential amplifier having a reference voltage input which is connected with a reference voltage source and a Q output of the first D flip-flop. This Q output, moreover, by way of a second delay arrangement having a delay time corresponding to the signal transit time through the second differential amplifier and the second D flip-flop, is connected with an output for a first binary signal. The Q output of the second D flip-flop is connected with an output for a second binary signal. Therefore, this solution is limited to the regeneration of quaternary signals.